Not Applicable.
Not Applicable.
1. Field of the Invention
The present invention relates in general to automotive cooling systems, and, more specifically, to a multi-port valve for controlling coolant flow to all cooling system components.
2. Description of the Related Art
Conventional cooling systems for internal combustion engines include a water jacket (i.e., passages within the engine block for circulating coolant), a radiator, a fan, a heater core, a water pump, and various hoses and clamps. They also include a thermostat and/or various valves to control the flow of coolant in response to the temperature of the coolant, demand for heating of the passenger compartment, and other factors.
When an engine is first warming up after being started, it is known to have the coolant flow bypass the radiator so that the coolant and engine warm up more quickly. Quicker warming leads to reduced engine emissions, improved fuel economy, and improved engine performance since reaching an optimal engine operating temperature in faster time means less time spent in cold start emissions mitigation strategies. The switching of coolant flow between a bypass circuit and the radiator circuit is conventionally performed by the thermostat. A typical thermostat uses a wax motor to drive a valve between one position in which all coolant is directed through the bypass and none to the radiator and another position in which all coolant is directed through the radiator and none through the bypass. Some thermostats may gradually cutoff bypass flow while radiator flow gradually increases.
Internal combustion engine technology is producing engines of higher efficiency and increasingly sophisticated control methods. This has increased the need for fast warm up times and precise control of engine operating temperatures, which have not been adequately attained with conventional cooling systems. Furthermore, delays in warming up of the engine also delay the availability of heat in the passenger compartment.
Separate from the thermostat, a passive 2-way valve may direct coolant to a heater core when warm air is being demanded in the passenger compartment. Other valves may also be included for either cooling or heating other vehicle components, such as cooling of electronic modules or heating of seats. Achieving these additional functions becomes expensive not only because of the proliferation of valves, but also because of the proliferation of separate actuators and the wiring, cables, or hydraulic or pneumatic (e.g. vacuum) lines required to control them.
The present invention provides a rotary valve for single point flow control of coolant resulting in advantages of shorter warm-up times, a lower pressure drop (reducing power consumption by the pump), reduced engine emissions and fuel consumption, improved cabin heater performance, and improved engine durability due to reduced thermal shocks to the engine components by virtue of more precise control of engine operating temperature.
In one aspect of the invention, a rotary valve for single-point coolant switching of coolant flowing in an engine cooling system comprises a valve body having an inlet port and a plurality of outlet ports. The outlet ports include a radiator port for allowing coolant flow in a radiator circuit, a bypass port for allowing coolant flow in a bypass circuit, and a heater port for allowing coolant flow in a heater circuit. A flow diverter is rotationally received in the valve body and includes a plurality of fluid passages providing predetermined flow paths between the inlet port and the outlet ports in response to a rotational position of the flow diverter. An actuator responds to a control signal for setting the rotational position. The predetermined flow paths include a first mode for distributing the coolant to the radiator port and the heater port while blocking coolant from the bypass port, a second mode for distributing the coolant to the bypass port while blocking coolant from the radiator port and the heater port, a third mode for distributing the coolant to the heater port while blocking coolant from the radiator port and the bypass port, and a fourth mode for distributing the coolant to the radiator port and the bypass port while blocking coolant from the heater port. In particular, the second mode may include a plurality of selectable flow rates to the bypass port including at least a first flow rate and a second flow rate higher than the first flow rate, wherein the first flow rate provides increased heat flow into the coolant. Thus, contrary to prior art thermostats, the slowest flow rate through the bypass may be achieved at the lowest coolant temperatures during engine startup.